1. Field of the Invention
This invention relates to a refrigerating apparatus provided with a scroll type compressor having a volume control mechanism.
2. Description of the Prior Art
A scroll fluid apparatus comprises an orbiting scroll member including an end plate and a wrap of an involute curve or a curve similar to the involute curve located in an upstanding position on the surface of the end plate, and a stationary scroll member including an end plate, a wrap of the same construction as that of the orbiting scroll member, a discharge port formed in the center of the end plate and a suction port formed in an outer peripheral portion, the orbiting and stationary scroll members being arranged in combination such that the surfaces of the respective end plates face each other with the wraps being in meshing engagement with each other. The apparatus further comprises a housing having a suction pipe and a discharge pipe connected thereto which usually contains the two scroll members.
An Oldham's ring is mounted between the orbiting scroll member and a frame or between the orbiting scroll member and the stationary scroll member for preventing the orbiting scroll member from rotating on its own axis, and the orbiting scroll member has a crank shaft in engagement therewith for moving the orbiting scroll member in orbiting movement while avoiding its rotation on its own axis, so as to compress gas in sealed spaces defined between the two scroll members and discharge the compressed gas via the discharge port. This type of scroll fluid apparatus serving as a scroll type compressor is disclosed in U.S. Pat. No. 3,884,599, for example.
The flow rate of the gas may vary depending on the specific volume of the gas drawn by suction into a suction space and the maximum sealed volume of the gas that is transferred from the suction space to the discharge space. The maximum sealed volume being constant, the flow rate would remain constant if the specific volume of the gas were constant.
Some problems are encountered when the scroll type compressor of the aforesaid construction is used as a compressor of a heat pump type refrigerating system. That is, since the volume of the compressor is constant as described hereinabove, changes in load that occur when the system is switched between a cooling mode and a heating mode should be coped with by effecting on-off control of the compressor.
Also, the cooling/heating ratio of a refrigerating system is lower than the ratio of the cooling load to the heating load. Thus when a heat pump type refrigerating system is designed to comform to the cooling load, the volume would not be enough for performing a heating operation, so that an auxiliary heating source would be required for operating the system to effect space heating.
To meet the aforesaid requirements, a scroll type compressor provided with a volume control mechanism has been developed and laid open to public inspection as Japanese Patent Laid-Open No. 28002/79, prior to the filing of this application. The specification of Japanese Patent Laid-Open No. 28002/79 discloses means for varying the suction air volume and the specific volume of the compressor by forming a groove on the surface of the end plate of the stationary scroll member for receiving therein a plunger which is moved in and out of the groove, to thereby provide a bypass passageway that can be opened and closed. However, there is no mention in the Japanese Patent Laid-Open No. 28002/79 of a system for effecting volume control of this scroll type compressor.